DE4446219A1 - Electric vehicle with independent multi-motor drives - Google Patents

Abstract

An electrically propelled vehicle is equipped with two electric motors (7,8) driving the wheels (3 to 6) via the differential gearing (9,10) and axles (1,2) supplied from the battery source (11). The controllers (21,22) collectively monitor and regulate the speed, direction and output torque of each motor (7,8) independently. The control require is designed to optimise total energy distribution and usage incorporating regenerative and/or resistive braking in addition to mechanical braking (12 to 15) depending on battery (11) condition and required retarding torque. A heating and ventilating unit (20) together with other electrical loads comprises a heat energy reservoir and a resistive sink and the system also offers an ABS refinement.

Description

The invention relates to a motor vehicle with the Merkma specified in the preamble of claim 1 len. Such a motor vehicle is, for example, from DE-OS 42 25 080 known. Here are several electromotives gates are provided for driving wheels, the Wheels are assigned to different vehicle axles. The motors are so controlled via a control device erbar that both a drive of the vehicle and a Braking with energy recovery can be done. It will both the speed, the torque and the direction of rotation of the engines are monitored and ABS algorithms are pre-selected been hit. The braking behavior is thus to be optimized which also includes conventional mechanical brakes are related.

The regenerative braking of motor vehicles under groove their electric drive motors is one Energy optimization common. Recovered energy will fed to a battery, increasing the range of the Vehicle is increased. When the battery is fully charged, the recovered energy can only be obtained through electrical Resistors are consumed, what is called a drag brake solution is called (example: DE-PS 30 32 603).

As also specified in DE-OS 42 36 093, the Concepts for electric vehicles Energy aspects in the foreground  reason, with an essential task always being stands to achieve a low vehicle weight and a optimized energy management both for the drive and to ensure even when braking. However, this could not yet be optimized. Both the An drive motors as well as the batteries and the mechanical ones Brakes are even larger than required is.

The object of the invention is to provide a motor vehicle Electric motors is powered, creating a optimized energy management with low vehicle mass should be achieved.

To solve this problem, the motor vehicle stands out according to the invention by the characterizing features of Claim 1 from. Other features of the invention are listed in claims 2 to 6.

There are several electric motors for driving wheels provided which different vehicle axles are arranged. The elec motors in both speed, torque and turning direction device can be monitored as well as independently of each other controllable that they are in drive mode, in generatori brake operation with energy recovery and in contrast motor braking work. Both in normal Drive operation as well as the counter-motor brake drive is an energy feed into the respective moto necessary. Compared to conventional motor vehicles of the type mentioned increases that of the electromo gates transferable braking power to the wheels, so that additional existing mechanical brakes smaller can be sioned as usual.

The wheels of different axles are mostly with under different braking torques. So it is  often possible, the electric motors to drive un wheels belonging to different axes in one un to operate in different operating modes. At least one Motor for the front axle wheels can brake against the engine sen while at least one motor for the rear axle wheels regenerative braking or vice versa. The generatori Energy recovered by the brakes can be used directly counter-motor braking engine are supplied. The named control unit optimizes this energy distribution and only then exposes additional electrical power the battery if necessary. The genera Toric energy is not first transferred to the battery fed in to gain with losses in chemical energy delt and then be removed again immediately. Alone Operating electrical consumers are di supplied with regenerative energy until it is completely used up. Only when this is back electrical energy gained exceeds the demand fed them to the battery. If this amount of energy The battery is also electri cal energy. As an electrical consumer who primarily those working in counter-motor braking tendency drive motors and heating and ventilation device tations of the motor vehicle taken into account.

The control device of the electric motors is in itself known way with setpoints that a Fah rer of the vehicle determined by a driving and / or Brake pedal (or switch) is operated. In addition is a signal connection between the control unit and a Brake control device provided that the entire vehicle braking controls and monitors. The brake control unit activates the mechanical brakes of the driver stuff if necessary. On the other hand, the total braking power by the electric motors and ge if necessary, the mechanical brakes are generated, opti lubricated and monitored, including the locking of the wheels  is excluded in as many operating states as possible. Since the engine and brake management here are very tight Related, only one control unit can both Drive control as well as the entire brake control take over. This is the tax mentioned at the beginning device combined with the brake control unit in one device.

The brake control unit or the uniform drive Brake control unit forms both the setpoint for the Brake force distribution on the individual vehicle axles as also target values for the braking forces of the individual wheels. The electric motors are switched on according to the specifications controls and an optimized energy distribution is before taken. Recovered ones not needed when braking Energy is one circuit, the other electri includes, fed, consumed there or supplied from there to the battery.

The fact that a compared to known electric vehicles enhanced electromotive braking is possible mechanical brakes less stressed and can easily be dimensioned. Regenerative when braking recovered energy is used more economically than so far.

The detailed description of the invention follows hand of an embodiment. The associated figure shows a drive-brake system of a motor vehicle the invention in a schematic representation.

In the figure, a motor vehicle is shown in the outlines ge, which has four wheels 3-6 distributed on two axles 1 , 2 . An electric motor 7 , 8 is provided for driving the wheels 3-6 of each axle 1 , 2 . Depending on the electric motor 7 , 8 , transmissions 9 , 10 (or a dif ferential) are assigned, and drive torques can be transmitted to the wheels 3-6 by transmission means, which are only indicated. An energy store 11 is arranged in the game between the axes 1 , 2 . It is referred to as battery 11 in the following. Due to the reversible process of converting chemical energy into electrical energy, the battery 11 is both electrical energy and can be fed into this. However, the processes of these energy conversions known per se are lossy.

Each wheel 3-6 of the motor vehicle mechanical brakes 12-15 are assigned to which wheel sensors are coupled. The brakes 12-15 can be operated in any way, the wheel sensors providing signals about the braking effect. These signals are also available when the mechanical brakes 12-15 are not actuated and can be evaluated.

In the figure, some selected electrical consumers of the motor vehicle are also indicated. These are specifically headlights 16 , 17 , rear lights 18 , 19 and a heating and ventilation system 20 .

In order to implement optimized energy management, a control device 21 for the electric motors 7 , 8 is provided, which is combined with a brake control device 22 . Setpoints for the operation of the motor vehicle can be specified by the vehicle driver via accelerator pedals 23 (or switches).

If the vehicle is to be accelerated positively or moved at constant speed, a corresponding command (illustrated by arrow 24 ) is transmitted from the accelerator pedal 23 to the control device 21 . Positive acceleration can take place in both the forward and reverse directions. It results in an increase in driving speed, which consumes energy, which in general (except possibly downhill) also applies when a command to keep the speed constant is transmitted. At the command of the control device 21 , the battery 11 electrical power is withdrawn as required (illustrated by the arrows 25 ). This electrical power is transmitted to the electric motors 7 , 8 (illustrated by arrows 26 , 27 in Rich direction of the motors 7 , 8 ). A fixed, but also a variable power distribution to the motors 7 , 8 can be provided, which has to be made dependent, for example, on the axle load distribution. Axle load sensors can be included in the control.

The electric power is converted into mechanical power by the drive motors 7 , 8 and transmitted to the wheels 3-6 . Since this type of vehicle drive is known per se, it is not dealt with in more detail here.

Commands to reduce the current driving speed (negative acceleration) are also transmitted from driving pedals 23 to the control device 21 . At the same time, the brake command is transmitted to the brake control unit 22 via an internal data link. Corresponding to an optimized braking force distribution on the axes 1 , 2 , control commands (illustrated by the arrows 28 , 29 ) are forwarded to the electric motors 7 , 8 . Depending on the braking power requirement, the electric motors 7 , 8 can either convert mechanical energy into electrical energy as a generator or can also be switched to a counter-motor drive. In the first case, the recovered energy (illustrated by the arrows 30 , 31 ) can be used in the vehicle, in the second case the motor 7 , 8 , which works in a counter-motor mode, must be supplied with energy (arrows 26 , 27 ). In contrast to the normal electric motor drive, a rotating field with counter-motor drive has an opposite direction of rotation to the direction of rotation of the rotor. Depending on the amount of electrical power supplied (arrows 26 , 27 ), the achievable braking torque is higher than when the motor 7 , 8 is in generator mode.

It is thus now possible to operate a plurality of electric motors 7 , 8 for driving a motor vehicle independently of one another in three different operating states. To accelerate the vehicle positively, electrical power from the battery 11 is consumed. Energy can also be consumed during negative acceleration (braking) or energy can be recovered.

In the event that at least one motor 7 or 8 energy is recovered, this is not supplied to the battery 11 or consumed via an electrical resistor, but this electrical power is distributed to other consumers. The electrical power to be recovered is preferably fed to motors 8 or 7 , which have a power requirement, that is to say operate in counter-motor braking mode. It is also possible to supply other consumers, such as the heating and ventilation system 20 or the lighting system 16-19 , with generically obtained energy.

A circuit 32 of the other electrical consumers is only indicated in the figure. The excess electrical power during engine operation is transmitted to this circuit (illustrated by arrows 33 ), electrical power not required being supplied to the battery 11 there (arrows 34 ). If the excess electrical power of the drive motors 7 , 8 does not meet the requirements of the circuit 32 , additional electrical power of the battery can be found here (arrows 35 ). Before electrical power is supplied to the battery 11 (arrows 34 ) or when it is fully charged, the entire energy requirement of the vehicle is covered. If necessary, electrical power can also be stored outside the battery 11 . For example, a heating core of the heating and ventilation system 20 can be strongly heated, which can be compensated for in the system 20 by appropriate flap control. Thereafter, the heating system 20 can be operated for a long time without Energiezu for heating. If the power requirement of the entire electrical system is fully covered and the battery 11 is fully charged, a motor 7 or 8 can in principle be operated from regenerative electrical power for counter-motor braking, even if no counter-motor braking would be required from the braking power requirement.

The mechanical brakes 12-15 of the vehicle are only used if the braking power to be applied by the motors 7 , 8 does not cover the braking power requirement. The braking commands specified via the pedals 23 correspond to a desired deceleration. The braking specified by the driver can be checked via the wheel sensors (arrows 36 ) and a speed signal to be supplied to the brake control unit 22 . Blocking of the wheels 3-6 is prevented by appropriate control of the motors 7 , 8 . If the braking power requirement is high, the mechanical brakes 12-15 are also activated (illustrated by arrows 37 ). Three types of brake control can be selected:

• 1. To achieve the maximum possible braking power of the motors 7 , 8 , electrical power can be taken from the battery 11 , the mechanical brakes 12-15 being protected as much as possible.
• 2. It is only generator-generated electrical power used for counter-motor braking of a motor 7 or 8 . The remaining braking requirements are covered by mechanical brakes 12-15 .
• 3. In energy-saving mode, the motors 7 , 8 only brake in generator mode. The mechanical brakes 12-15 are loaded relatively high.

Using a short numerical example for brake control variant 2 . the above should be clarified:
The vehicle has, according to a certain axle load distribution and shift, for example, a braking power requirement on the front axle 1 of P _v = 29.5 kW and a braking power requirement on the rear axle 2 of Ph = 15.8 kW. The wheels 5 , 6 of the rear axle 2 are braked counter-motor, for which purpose the motor 8 has a power requirement of approximately P _el-h = 17.2 kW. The wheels 3 , 4 of the front axle 1 are regeneratively braked in such a way that the electrical power P _el-v to be recovered covers the power requirement P _{el-h of} the motor 8 . About 18.7 kW braking power can be generated in the front, the 17.2 kW electrical power for the motor 8 in the motor 7 being recovered. The missing 10.8 kW braking power for the wheels 3 , 4 of the front axle 1 must be applied by the mechanical brakes 12 , 13 .

In another control example, the rear axle 2 could be braked completely by the motor 8 as a generator, whereby approximately 14.5 kW of electrical power P _{el-h would be} released. Thus, a counter motor Bremslei stung for the front axle 1 of about 13.4 kW can be generated via the motor 7 . The lack of braking power (16.1 kW) is to be applied by the mechanical brakes 12 , 13 .

Depending on the state of charge of the battery 11 , power consumption in the electrical system of the vehicle, road and load conditions, various control variants are possible, which result from the fact that the motors 7 , 8 have both braking and regenerative braking power on the wheels 3- 6 can transfer.

In another, not shown embodiment of the invention also individual wheels of associated electric motors are driven. For example, the wheels of the Front axles each equipped with independent wheel drives and the wheels of the rear axle are made by only one Motor driven or braked together. It is the same possible, only one drive motor for both front wheels and to provide one motor for each rear wheel or all four wheels with independent wheel drives prepare. In any case, the three or four electric motors independently in the three possible Operating modes controlled. Thus the drive system better than known designs to support the Vehicle steering, traction control and one Anti-lock braking system are used, which is energy management can be optimized very variably. Electronic Motor controls have the ability to very quickly to changed operating conditions due to changed engine control to respond.

Claims (6)

1. Motor vehicle with several electric motors ( 7 , 8 ) for driving wheels ( 3-6 ), which are assigned to one or more vehicle axles ( 1 , 2 ), with at least one battery ( 11 ) and with a control device ( 21 , 22 ) for setting and monitoring the speed, direction of rotation and torque of the electric motors ( 7 , 8 ), characterized in that the electric motors ( 7 , 8 ) by the control device ( 21 , 22 ) operate independently of one another on a drive a regenerative braking operation with energy recovery or a counter-motor braking operation can be set. 2. Motor vehicle according to claim 1, characterized in that the electrical power obtained in the regenerative braking operation of an electric motor ( 7 , 8 ) other electrical consumers ( 7 , 8 , 16-20 ) in the motor vehicle and / or in the battery ( 11 ) can be stored, with electrical consumers ( 7 , 8 , 16-20 ) preferably operating in the drive system or in counter-motor braking operation working electric motors ( 7 , 8 ) are taken into account. 3. Motor vehicle according to claim 2, characterized in that in addition to the preferably controlled Elek tromotoren ( 7 , 8 ) in drive mode or counter-motor braking operation as further electrical Ver heating and ventilation devices ( 20 ) and lighting devices ( 16-19 ) with generatori electrical power obtained. 4. Motor vehicle according to claims 1 to 3, characterized in that the control device ( 21 , 22 ), the electrical power generated by at least one electric motor ( 7 , 8 ) primarily over the electrical power stored in the battery ( 11 ) to the electrical power Distributed to consumers ( 7 , 8 , 16-20 ). 5. Motor vehicle according to claims 1 to 4, characterized in that the control device ( 21 ) has a signal connection to a brake control device ( 22 ) of the motor vehicle. 6. Motor vehicle according to claims 1 to 5, characterized in that the brake control unit ( 22 ) both a braking force distribution to the different
Vehicle axles ( 1 , 2 ) and on the individual wheels ( 3-6 ) can be regulated, the vehicle being able to be braked both by the electric motors ( 7 , 8 ) and by mechanical wheel brakes ( 12-15 ).